The microstructure of Ti/Au contacts on n-type GaN annealed in nitrogen

Ti(40nm)/Au(120nm) contacts have been prepared on n-GaN/sapphire. The contacts were annealed from 400?C to 900?C for 10min in nitrogen, respectively. The interaction between the contact metallization and the GaN epitaxial layer (on sapphire) was investigated by electron microscopy and X-ray diffraction. It was found that for an annealing at a temperature equal or higher than 700?C, the gold diffused through Ti layer and Au-rich grains were formed under this Ti layer. Between the Au-rich grains and the n-type GaN layer a new Ti-rich thin layer was identified by XTEM. High resolution images and X-ray data showed that it is TiN0.26 that was formed at the metal/semiconductor interface. FESEM investigations showed that Ti/Au contacts annealed in nitrogen still have a very smooth surface morphology. Ti(40nm)/Au(120nm) contacts have been prepared on n-GaN/sapphire. The contacts were annealed from 400?C to 900?C for 10min in nitrogen, respectively. The interaction between the contact metallization and the GaN epitaxial layer (on sapphire) was investigated by electron microscopy and X-ray diffraction. It was found that for an annealing at a temperature equal or higher than 700?C, the gold diffused through Ti layer and Au-rich grains were formed under this Ti layer. Between the Au-rich grains and the n-type GaN layer a new Ti-rich thin layer was identified by XTEM. High resolution images and X-ray data showed that it's TiN0.26 that was formed at the metal/semiconductor interface. FESEM investigations showed that Ti/Au contacts annealed in nitrogen still have a very smooth surface morphology.